5/21/19 1 Focus of Chapter 15: Pathways • Pathway defined: set of nerves, nuclei, and tracts taken by an impulse • Sensory Pathways • Somatic Motor Pathways • Autonomic (visceral) Motor pathways- Chapter 16 Sensory receptors are connected to the CNS • Impulses sent to CNS are – filtered at thalamus – projected to cerebral cortex • Sensation: arriving information • Perception: conscious awareness of sensation • Transduction: conversion of stimulus to an action potential Sensory pathways • Types – Somatic sensory pathways – Visceral sensory pathways • Origins: receptors • Destinations: – Somatic sensory pathways • Primary sensory cortex • Cerebellum – Visceral sensory pathways • Brainstem • Diencephalon
5/21/19 2 Labeled line • Sensory impulses travel along a labeled line – a link between receptor and a cortical neuron in cerebrum • Carry one modality – Pain, cold, etc. • Use this idea to understand – Phantom limb pain later L in e d raw in g o f th e p ain sy stem b y L o u is L a F o rg e, 1 6 0 0 ’s Interpretation of sensory information • Axons are organized in bundles with specific origins and destinations • Where a stimulus arrives on sensory cortex determines its perceived location • Frequency of action potentials determines intensity of stimulus Organization of Somatic Sensory Pathways • Sensory pathways consist of 3 neurons – First order neuron – Second order neuron – *Third order neuron; • * n o t a lw a y s p r e s e n t – Labeled line • Axon collaterals may exist – Not pictured – send impulses to cerebellum, reticular formation, etc.
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- Spring '18
- Mark Bolke
- Corticospinal tract, Visceral Sensory Pathways